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Full text of "Treatise On Applied Analytical Chemistry(Vol-1)"

AMMONIUM THIOCYANATE

47

AMMONIUM   PERSULPHATE
NH4S04 = 114

Colourless crystals, alterable in moist air, soluble in water. The aqueous
solution decomposes slowly with evolution of oxygen, and rapidly when
heated with an acid ; it decomposes potassium iodide solution, liberating
iodine. It always contains more or less marked quantities of ammonium
bisulphate, moisture, and alkali, its value depending on its content of the
persulphate.

1.  Determination of the Persulphate (Ulzer's method).—0-3 gram
is dissolved in about too c.c. of water in a flask with a stopper fitted with
a Bunsen valve and the liquid boiled for about 30 minutes with excess of
ferrous ammonium sulphate (1-1-5 gram) and dilute sulphuric acid.    The
excess of ferrous salt is then titrated with standard permanganate (i c.c.
N/io-permanganate = 0-0114 gram of NH4S04).

The persulphate may also be determined iodometrically. According
to Mondolfo, 2-3 grams of the persulphate are dissolved in 100 c.c. of cold
water and 10 c.c. of the solution heated for 10 minutes in an oven at 60-80°
with an excess (0-25-0-5 gram) of potassium iodide (puriss.) in a small
bottle with a ground stopper. The iodine liberated is titrated with N/io-
thiosulphate and starch paste (i c.c. N/io-thiosulphate = 0-0114 gram

NH4S04).

From the amount of persulphate present, the active oxygen which a
commercial persulphate can furnish may be calculated, knowing that i
part of NH^SO,! = 0-07 part of oxygen.

2.  Other  Determinations.—Complete analysis  includes  determina-
tions of:  (a) the total sulphuric acid, by precipitation with barium chloride
after the persulphate solution has been boiled with hydrochloric acid until
the persulphate is completely decomposed ;   (b) the total ammonia, by one
of the ordinary methods (see Fertilisers) ;   (c) the acidity, by titrating a
solution of the persulphate, made in the cold, with N-alkali and methyl
orange ;   (d) the fixed residue after calcination.    From the total sulphuric
acid is subtracted that combined with the ammonia as persulphate (i) and
from the total ammonia that in the form of persulphate; if sulphuric acid
and ammonia remain, they arc regarded as existing as ammonium bisulphate.

In the same way potassium persulphate, KSO4 == 135-1, is analysed.

AMMONIUM   SULPHATE
(See Fertilisers)

AMMONIUM   THIOGYANATE
(Ammonium Sulphocyanide)

NH4CSN = 76

Colourless, deliquescent crystals, extremely soluble in water or alcohol.
Its analysis includes tests for certain impurities (sulphates, iron, lead) and
determinations of the proportions of thiocyanic acid and ammonia.a.cid